CA1235482A - Magnetic transducer head utilizing magnetoresistance effect - Google Patents

Abstract

ABSTRACT

A magnetoresistance effect type magnetic transducer head apparatus comprises a magneto resistance effect sensing element, means for applying high-frequency magnetic field to the sensing element, means for taking-out output signal from the sensing element, a filter for taking-out the high-frequency component of the output, and another filter for rectifying the output and taking-out the low-frequency component. The magnetic head apparatus may be constituted as digital circuit and the multi-channel apparatus can be easily implemented.

Description

~LZ3S9~

BACKGROUND OF THE INVENTION

Field of the Invention The present invention relates is magnetic transducer head magneto resistance effect, and more particularly to a magneto resistance effect type magnetic head apparatus characterized by bias means.

BRIEF DESCRIPTION OF THE DRAWINGS

Fig. lo is an enlarged sectional view of essential part of an MY magnetic head apparatus of yoke type;
Fig. lo is a plan view of the magnetic head apparatus in Fig. lay Fig. 2 is an enlarged sectional view of essential part of an MY magnetic head apparatus of shield type;
Fig. 3 is a diagram illustrating constitution of an MY magnetic head apparatus in tube prior art;
Fig. 4 is a diagram of MY characteristic curve illustrating operation of an MY head apparatus in the prior art, Fig. 5 is a diagram illustrating constitution of an MY head apparatus as another example in the prior art;
Fig. Ç is a diagram illustrating constitution ,~,~,' of an OR magnetic head apparatus as an embodiment of the invention;
Fig. PA is a diagram of MY characteristic curve illustrating operation of the OR magnetic head apparatus of the invention;
Fig. 7B is a diagram illustrating operation of the MY magnetic head apparatus of the invention;
Fig. PA - C is a waveform chart illustrating operation of the MY magnetic head apparatus of the invention;
Fig. 9 is a diagram illustrating constitution of an MY magnetic head apparatus as another embodiment of the invention;
Fig. 10 is a diagram of MY characteristic curve illustrating operation of the magnetic head apparatus in Fig. 9;
Fig. 11 is a diagram illustrating constitution of an MY magnetic head apparatus as another embodiment of the invention;
Fig. AYE - E is a waveform chart illustrating operation of the magnetic head apparatus in Fig 11;
Fig. 13 is a diagram illustrating constitution of an MY magnetic head apparatus as another embodiment ,.. ..

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of the invention;
Fig. 14 is an equivalent circuit diagram of the protozoa in jig. 13;
Fig. 15 is diagram illu~rating distrain factor char~cteri~tic~;
Figs. 16, 17, lo and 19 are diagrams illustrating constitution ox OR magnetic head apparatuses as other embodiments of the invention;
Fig. AYE, B is a waveform chart illustrating operation of the above apparatuses;
Fig. 21 and Fig. 23 are diagrams illustrating constitution of MY magnetic head apparatuses as further embodiments of the invention; and Fig. AYE - C end Fig. AYE - F are waveform charts illustrating operation of the MY magnetic head apparatus in Fig. 21 and Fig. 23 respectively.

Description of the Prior Art A magneto resistance (hereinafter referred to as MY effect) effect type magnetic head apparatus has a head member h with structure as shown in Fig. lo and Fig. lo. Fig. lo is a sectional view of essential part of an MY head, and Fig. lo is a plan view thereof. On a magnetic substrate 1 of Nissan ferrite or Mn-Zn ferrite, or through an insulating layer 2 of Sue etc. on the ~2:~5~Z

substrate 1 if it is conductive, a bias conductor 3 of band-shaped conductive film it applied and constitutes a bias magnetic field generating current passage to apply a bias magnetic field to an MY sensing element as hereinafter described. An MY sensing element 5 comprising MY magnetic thin film on Nephew alloys or Nix Co alloys is arranged on the bias conductor 3 through an insulating layer 4. A pair of magnetic layers 7 and 8 of My permalloy or the like to constitute a magnetic core of part of a magnetic circuit are formed so that the magnetic layers 7 and 8 ride at each one end on the MY sensing element 5 through a thin insulating layer 6 and extend across the bias conductor 3 and the MY
sensing element I A protective substrate 10 is provided to the substrate 1 through a non-magnetic protective layer 9. An operating magnetic gap g is formed between one magnetic layer 7 and the front end of the substrate 1 through a non-magnetic gap spacer layer 11 comprising, for example, the insulation layer 6 having a required thickness. Front surface of the substrate 1, the gap spacer layer 11, the magnetic layer 7, the protective , . --.

3~Z

layer 9 and the protective substrate 10 is polished thereby an opposing surface 12 to a magnetic recording medium is formed for the magnetic gap g to face thereto.
The rear end of the magnetic layer 7 which constitutes the magnetic gap g and the front end of other magnetic layer 8 are formed to ride on the MY sensing element 5 through the insulating layer 6, and both ends are spaced from each other by a discontinuous portion 13. The rear end of the magnetic layer 7 and the front end of the magnetic layer 8 are electrically insulated from the MY
sensing element 5 by the insulating layer 6 but magnetically connected. The discontinuous portion 13 between both magnetic layers 7 and 8 is magnetically connected by the MY sensing element 5, so that a magnetic circuit is formed around the substrate 1 -the magnetic gap g - the magnetic layer 7 - the MY sensing element 5 - the magnetic layer -the substrate 1.
Fig. 2 shows an enlarged sectional view of an MY type head apparatus of so-called shield type as another example. In the head apparatus of Fig. 2, a bias conductor 3 and an MY sensing element 5 opposed thereto are disposed between high permeability magnetic bodies 60 and 61 such as ferrite through a non-magnetic ,, .

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layer 62, and one end surface is polished so as to form a tape opposing surface 12.
In such MY type magnetic head apparatus, signal magnetic flux from the front gap g opposed to the magnetic recording medium flows in the MY element through the above-mentioned magnetic circuit in case of the MY head of Fig. lay or directly in the MY element in case of Fig. 2, thereby resistance value of the MY
sensing element 5 varies in response to the external magnetic field by the signal magnetic flux. Variation of the resistance value is detected as voltage variation across the MY sensing element 5 while sensing current flows through the MY sensing element 5 thereby reproduction of the recording signal on the magnetic recording medium is effected. In this case, the MY
sensing element 5 must be magnetically biased in order that the MY sensing element 5 acts linearly as magnetic sensor and has high sensitivity. The bias magnetic field is applied by magnetic field generated by energizing the bias conductor 3 and magnetic field generated by the detecting current itself flowing through the MY sensing element 5.
In the MY type magnetic head apparatus as ~Z35~2 clearly seen in a schematic constitution of Fig. 3, the MY sensing element 5 is applied with the magnetic field generated while prescribed do current it flows through the bias conductor 3, and at the same time prescribed sensing current imp flows through the MY sensing element 5. In such state that the MY sensing element 5 is applied with the bias magnetic field Ho composed of the magnetic field generated by energizing the bias conductor 3 and the magnetic field generated by the detecting current flowing through the MY sensing element 5. In such bias condition the signal magnetic field HO
is applied from the magnetic recording medium. Voltage cross the MY sensing element 5 on the basis of resistance variation by the signal magnetic field Ho, i.e. variation of potential at point A is amplified by an amplifier 14 and detected at an output terminal 15.
Numeral 16 designates a coupling condenser.
Fig. 4 shows a working characteristic curve of the MY sensing element 5 illustrating relation between the magnetic field H and the resistance value R. It is clear from Fig. 4 that the resistance R follows parabolic curve being convex upwards in the range of the magnetic field H being small in absolute value, i.e.

~354~Z

-HER BRIE but the resistance R becomes apart from the parabolic curve and gradually approaches to value Ruin when magnetization of the MY magnetic thin film at center portion becomes saturated in the magnetic circuit direction Maximum value Max of the resistance R means state that the magnetization of the MY magnetic thin film is directed entirely to the current direction. The bias magnetic field HUB is applied at characteristic portion according to parabolic curve in the working characteristic curvier and signal magnetic field shown by numeral 17 in Fig. 4 is Applied from the magnetic recording medium. Then corresponding to the signal magnetic field, output according to variation of the resistance value as shown by numeral lo in Fig. 4 is obtained. In this case, however, the more the signal magnetic field, the more the second harmonic distortion.
In the MY type magnetic head apparatus, potential at point A of Fig. 3 is determined by composition of fixed component and variable component of the resistance in the MY sensing element 5. Since the fixed component in this case attains to about 98% and is largely dependent on temperature, the temperature drift of the potential at point A becomes large. The _ g _ US

resistance value R in the MY sensing element 5 is represented by following f formula .

R = Roil + cost) (1) wherein Row stands for fixed component of resistance, stands for maximum resistance variation factor, stands for angle between current direction and magnetizing direction in the MY sensing element 5.
For example, if the MY sensing element 5 is an MY
magnetic thin film of BlNi-19Fe alloy (permalloy) with thickness 250 A, the measured value of becomes about = 0.017. The value of in this case is dependent more or less on thickness or material of the MY magnetic thin film of the MY sensing element 5, and becomes about = 0.05 at most On the other hand, Row is represented by following formula.

Row = I a t) (2) Jo ~2354~2 wherein Rip stands or initial value of resistance, a stands for temperature coefficient, it stands for temperature variable component.
The measured value of the temperature coefficient a in the above example of the MY tensing element 5 is about a = 0.0027/deg. This may produce large noise at detecting the do magnetic field. In order to avoid the temperature dependence in the MY magnetic head apparatus in usual, differential constitution to cancel the temperature dependence must be inevitably taken.
Moreover, in such MY type magnetic head element, since the temperature coefficient is large as above described, for example, when heat generated by energizing the MY sensing element 5 or by the bias current flowing through the bias conductor 3 is radiated unstably at rubbing of the heat element with the magnetic recording medium thereby the head temperature varies, large noise, so-called rubbing noise may be produced.
If the amplifier 14 in Fig. 3 has low-impedance input, assuming that the cut-off frequency by the capacitor 16 be fox the required capacitance C for the capacitor 16 becomes ~;~354~82 C = I (3) wherein JO = foe If the MY sensing element 5 is made of the permalloy with thickness of 250 A and length of 50~ m, the resistance value R becomes about 120 . If fox = Liz the value of C must be as large as C = 1.3 F. This becomes problem particularly when the magnetic head apparatus of multi-track type is formed.
Permeability in a magnetic circuit, particularly that in the magnetic layers 7 and 8 having relatively small thickness end sectional area, is preferably as large as possible. Since the permeability becomes maximum when the external magnetic field is zero, application of the above-mentioned bias magnetic field lowers the permeability.
The above mentioned MY type magnetic head apparatus in do bias system is advantageous in that the effective track width is large and a narrow track is 1~35~

easily implemented. On the contrary, it is disadvantageous in that the linearity is bad, the do reproduction it difficult, the rubbing noise is large, the Barkhausen noise is large, and dispersion of the output is large.
In the prior art, an MY type magnetic head apparatus par ocularly to remove second harmonic distortion of the output signal has been proposed. Such magnetic head apparatus will now be described referring to Fig. 5. A head member h is composed of an MY sensing element 5 with the neutral point grounded and two parts pa, 5b having equal characteristics and of a bias conductor 3 with the neutral point grounded and two parts pa, 3b having equal characteristics. Both ends of the MY sensing element 5 is supplied with the same detecting current imp in reverse directions from each other, and both ends of the bias conductor 3 is also supplied with the same do current it in reverse directions from each other. Thus, the parts pa, 5b in the MY sensing elements 5 are applied with the bias magnetic field HUB in reverse directions from each other on the basis of the magnetic field generated by the do current it flowing through the two parts pa, 3b of the ~2;3 5D~8~

bias conduct 3 and the magnetic field generated by the detecting current imp flowing through the MY sensing element 5 and also with the same signal magnetic field from the magnetic recording medium. Voltage across the MY sensing element 5 based on the resistance variation by the signal magnetic field Ho that is, variation of potential at points Al, A, is supplied to a differential amplifier 14'. In this constitution, the points Al, A have output voltages in inverted phase from each other but second harmonics in the same phase, thereby output signal with little distortion by removing the second harmonics is obtained at output side of the differential amplifier 14', i.e. at an output terminal 15.
However, the MY type magnetic head apparatus of Fig. S in the prior art has hollowing disadvantages.
Since equalization of characteristics at the two parts pa, 5b of the MY sensing element 5 in high accuracy is difficult and equalization of the magneto field to the two parts pa, 5b of the MY sensing element in high accuracy is also difficult, offset may be produced in the output signal. Since non-sensitive region is produced at the border between two parts of the MY

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sensing element 5, width of the head element 5 cannot be narrowed appreciably and therefore the multi-channel apparatus cannot be easily implemented. Increase of the number of lead for the element also makes difficult the implementation of the multi-channel apparatus.
A MY type magnetic head apparatus of barber pole type also has been proposed. In this apparatus, a number of conductor bars of gold or the like in parallel to each other are adhered to the MY sensing element in the MY type magnetic head element in oblique direction to the longitudinal direction of the MY sensing element.
The MY magnetic apparatus of barber pole type is advantageous in that dispersion of the output is little and the circuit may be constituted by an amplifier only. On the contrary, it is disadvantageous in that the do reproduction is difficult, the rubbing noise is large, the narrow track cannot be implemented easily, and the effective track width is not very large.

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OBJECTS AND SUMMARY OF THE INVENTION

It is an object of the present invention to provide an improved magnetic transducer head utilizing magneto resistance effect which overcomes the prior art drawbacks.
It it another object of the present invention to provide a magnetoresis~ance effect type magnetic transducer head superior in linearity of the response.
It is further object of the present invention to provide a magneto resistance type magnetic transducer head having improved second harmonic distortion.
It is still further object of the present invention to provide a magneto resistance effect type magnetic transducer head improved in temperature stability.
It is yet further object of the present invention to provide a magneto resistance effect type magnetic transducer head having an improved dynamic range.
It is still another object of the present invention to provide an improved multi-channel magnetic transducer head utilizing magneto resistance effect.

~235~82 According to one aspect of the present invention, there is provided a magnetic transducer head utilizing magneto resistance effect which comprises a magneto resistance effect sensing element sensing a signal magnetic field on a traveling magnetic recording medium, means for applying high frequency magnetic field to said sensing element, means for obtaining an output from said sensing element, means for rectifying said output and low pass filter means supplied with said rectified signal for deriving an output corresponding to said signal magnetic yield.
According to another aspect of the present invention, there is provided a magnetic transducer head utilizing magneto resistance effect which comprises a magneto resistance effect sensing element sensing a signal magnetic field on a traveling magnetic recording medium, means for deriving high frequency signal, means for applying high frequency magnetic field synchronized with said high frequency signal to said sensing element, means for obtaining an output from said sensing element, means for multiplying said output with said high frequency signal to derive a multiplied signal, and low pass filter means supplied with said 3 23~82 multiplied signal for deriving an output corresponding to said signal magnetic field.

Description OF TIE PREFERRED DOMINATES

An MY type magnetic head as on embodiment of the invention will now be described referring to Fig. 6.
In the embodiment, since an MY type head element h has - ~23S~1~2 similar constitution to that described in Fig. 1 and Fig. 3, parts in Fig. 6 corresponding to Fig. 1 and Fig. 3 are designated by the same reference numerals and the repeated description shall be omitted. In a bias conductor 3 of the head element h of the embodiment, small arc. bias current it Of high frequency lo flows in superposition to do bias current it thereby high frequency magnetic field is applied to an MY sensing element 5. Where waveform of the arc. bias current it hence waveform of the arc. magnetic field may be sinusoidal or rectangular. Thus the MY sensing element 5 is applied with the arc. bias magnetic field in superposition to the do bias magnetic field thereby arc. signal of frequency lo is taken out across the MY
sensing element 5, i.e. at point A in Fig. 6. Fig. 7 shows operation when the do bias magnetic field HUB, the signal magnetic field Ho and the arc. bias magnetic field HA are superposed. If variation OH of the arc.
bias magnetic field HA is small, amount of resistance variation AR to the variation of the arc. bias magnetic field at a moment is obtained as absolute value of differential of a curve in Fig. PA. Since this is the differential of the parabolic curve, variation of ~%35~

resistance as output to amount of the do bias magnetic field HUB and the signal magnetic field Ho becomes linear in principle as shown in Fig. 7B. Consequently, amount of the arc. signal obtained at the point A in Fig. 6 becomes output which varies corresponding to sum of the do bias magnetic field HUB and the signal magnetic field from the magnetic recording medium. As shown in Fig. 6, the output at the point A passes through an amplifier 19 to pass the above-mentioned frequency component lo and is rectified by a rectifier 20 and then passes through a low pass filter 21 thus output is taken out corresponding to the signal magnetic field from the magnetic medium. If the final output obtained at an output terminal 15 must have frequency band 0 - 100 kHz, the frequency lo of the arc. current it may be made much higher than the frequency band, for example, lo = 1 MHz.
In this case, low cutoff frequency of the amplifier 19 is selected higher than 100 kHz and lower than the lo 1 MHz, for example 500 oh Output from the high pass filter 19 is rectified by the rectifier 20 and then passes through the low pass filter 21 with cutoff frequency 100 kHz as already described. Thus signal of the frequency band 0 -100 kHz is obtained.

~3S~2 In the magnetic head apparatus of such constitution, if external magnetic field signal magnetic field + bias magnetic field) shown in Fig. PA
is applied -to the MY sensing element 5, output shown in Fig. 8B, where carrier of the frequency lo is amplitude-modulated by signal, is obtained at point B in Fig. 6, and output corresponding to the signal magnetic field as shown in Fig. 8C is taken out at the output terminal 15.
In the magnetic head apparatus of the invention, since output of linear operation characteristics of the MY sensing element 5 corresponding to the differential of the original operation characteristics curve of second order is taken out, the distorsionless reproduction signal can be obtained.
Even if fixed component of resistance of the MY sensing element is largely dependent on temperature, the invention working according to characteristics of the differential of the performance characteristics curve of the MY sensing element can eliminate the influence of the temperature dependence of the fixed component and reduce the temperature drift significantly.

~23~

Since the temperature dependence of the fixed component of resistance of the MY sensing element 5 is eliminated as above described, noise caused by rubbing with the magnetic recording medium can be improved.
Further, since a capacitor 16 of the invention may only pass the frequency lo, if lo = 500 kHz for example, capacitance C of the capacitor 16 may be C =
2600 pi. If the lo is further increased, the capacitance C may be further reduced.

Fig. 9 is a constitution diagram of an MY type magnetic head as another embodiment of the invention.
Parts in Fig. 9 corresponding to Fig. 6 are designated by the same reference numerals and the repeated description shall be omitted. In this case, a bias conductor 3 is not supplied with do bias current but with arc. bias current it only. Fig. 10 shows the operation schematically. In Fig. 10, real R - H
operation characteristics curve is shown by solid line, and extrapolation of parabolic curve portion of the characteristics is shown by broken line and the magnetic field indicating the minimum resistance value Ruin in ~%3~48Z

the extrapolation becomes who and -Ho As shown in Fig.
10, arc. bias magnetic field HA in superposition to signal magnetic field US is applied in the embodiment.
The resistance variation of an MY sensing element S in response to the arc. bias magnetic field is obtained corresponding to polarity and intensity of the signal magnetic field.
In this case, the MY operation characteristics curve is parabolic curve, and the resistance value Rmr of the MY sensing element is represented as follows:

Rmr = Max aRmax H (4) where Max = Max Ruin. The magnetic field H is applied to the MY sensing element 5. The magnetic field H is represented by sum of the bias magnetic field HA
(t) and the signal magnetic field Ho (t) as follows:

. j .
Hut) = HA + HO (5) where the HA is generated by the bias conductor 3 and set to (t) = HA sin I t) (6) ~L~354~3%

where I = I lo (7) If the MY detecting current is represented by I, output TV of the MY sensing element 5 becomes TV = I Rmr (8) From above formulae (4), (5), (6), it follows that TV = I Max - I Ho x AYE sin t + assay (t) x Senate) + (HS(t))2} (9) Next, the TV and signal having the same phase and frequerlcy as that of the arc. bias magnetic field HA, e.g. sin (it), are multiplied by a multiplier 200 The multiplication output Vet becomes Vet = Vicinity) = I Rmax-Sin(~t) Max {HA0 Sin (it) + AYE Ho Senate) + (Hs(t))2} into) (10) - I -~235~

Then the output Vz passes through a low pass filter 21, terms having component in formula (10) are eliminated.
It follows therefore that I; ax Senate) -I 0 (11 _ . .. . . .. .
HOWE Senate) = 2 {Sin(~t)-cos(2~t) x Senate)} 0 _ (12) assassinate) = HO Ho {l-cos(2~t)~ Hess (13) thy} Senate) 0 (14)l Consequently, output voltage Vow obtained at a terminal 15 becomes Vow = Jo Max I H it) (15) x rut 2 Lo thus voltage proportional to the signal magnetic field HO is obtained. Even if the signal magnetic field component HO is contained in the input to the multiplier 20, it does not appear in output in this case. Consequently, the amplifier 19 is not necessarily

- 2 5 -~L2354~3Z

always required.
According to the above constitution, output corresponding to polarity of the external magnetic field can be taken out. In addition to advantages similar to those in the previous embodiment, this constitution is advantageous in that the dynamic range becomes large.
Further in this case, if the magnetic bias is made arc.
component only, decrease of permeability of the magnetic circuit caused by the do bias magnetic field can be avoided.

A third embodiment of the invention will now be described in detail referring to Fig. 11.
Constitution of an MY type magnetic head element h is similar to Fig. 1 and Fig. 3. Numeral 26 designates a rectangular wave generator, and frequency of the rectangular wave signal is selected to three times or more of the maximum frequency of the signal magnetic field do field will do). The rectangular wave signal is supplied to a buffer amplifier (current driver) 27 r and output of the buffer 27 permits bias current it Of rectangular wave to flow through a bias ~235~2 conductor 3.
When bias magnetic field HUB is applied by the rectangular wave magnetic field generated by the rectangular wave current it flowing through the bias conductor 3 and the magnetic field generated by to detecting current imp flowing through the MY sensing element 5, the signal magnetic field Ho from the magnetic recording medium is applied to the MY sensing element 5. Variation of voltage across the MY sensing element 5 based on resistance variation by the signal magnetic field Ho, i.e. variation of potential at point A, is taken out by a signal taking-out means 30 where the signal is supplied through a coupling capacitor 16 to an amplifier 19 and amplified. Output of the amplifier 19 is supplied to a phase converter changing circuit 31 where the output of the amplifier 19 is phase-inverted alternately in non-inverted phase and inverted phase according to the rectangular wave signal from the rectangular wave generator 26. More specifically, output of the amplifier 19 and output inverted by an inventor I are alternately supplied by a switch 25 controlled by the rectangular wave sign alto a low pass filter 26 and signal output corresponding to ~2354 !32 the signal magnetic field Ho is obtained at an output terminal 15.
Next, operation of the magnetic head apparatus of Fig. 11 will be described referring also to Fig. 12.
Fig. AYE shows characteristicslcurve of resistance versus magnetic field in the MY sensing element 5.
Since the MY sensing element 5 is applied with the magnetic field in superposition of the signal magnetic field HO and the rectangular wave bias magnetic field HUB with relatively large level as shown in Fig. 12B, output voltage TV being asymmetric to positive or negative polarity as shown in Fig. 12C is obtained from the MY sensing element 5. If the output voltage Vet) is changed alternately to non-inverted phase or inverted phase by the phase converter changing circuit 31 in synchronization with the rectangular wave bias magnetic yield Hug, signal output Vow corresponding to the signal magnetic field HO in Fig. 12B is obtained to output side of the low pass filter 21, i.e. the output terminal 15.
Above-mentioned MY type magnetic head apparatus comprises the magneto resistance effect sensing element 5 to which signal magnetic field is applied, the ~2359L8Z

bias magnetic field generating means 3, 26, 27 to apply the magnetoreslstance effect sensing element 5 with rectangular wave bias magnetic field of prescribed frequency, the signal taking-out means 30 to take out output signal corresponding to the signal magnetic field from the magneto resistance effect sensing element I, the phase converter 31 which receives output signal from the signal taking-out means 30 and generates signal of non-inverted phase and inverted phase alternately in synchronization with the rectangular wave bias magnetic field, and the low pass filter 21 to which output signal of the phase converter 31 is supplied. According to the MY type magnetic head apparatus in such constitution, offset is not produced in the output signal, the apparatus can be easily formed in multi-channel structure, and distortion is reduced by eliminating second harmonics of the output signal.
Further in the MY type magnetic head apparatus, noise caused by rubbing against a tape is hardly generated not easily produced, and even if a capacitor ox the signal taking-out means has small capacitance signals up to do signal can be taken out.
It seems in the MY type magnetic head ~23~ Z

apparatus of Fig. 3 that rectangular wave bias current flows through the bias conductor 3, signal output from the signal taking-out means is multiplied with rectangular wave signal in synchronization with the bias current, and the multiplication output is supplied to the low pass filter, thereby signal output corresponding to the signal magnetic field is obtained. However, such constitution has disadvantages as follows:
A filter must be provided to eliminate signal component caused by variation of fixed component of the resistance in the MY sensing element 5, or otherwise rectangular wave current must be supplied to a resistor having the same resistance value as that of the fixed component of the resistance in order to subtract signal corresponding the voltage across the resistor from the signal output and to cancel the signal component caused by variation of the fixed component of the resistance.
An amplifier of wide dynamic range is required. The low pass filter must have sharp cut-off property. However, the embodiment does not have any of such disadvantages.

A fourth embodiment of the invention will now glue be described referring to Fig. 13. The embodiment relates to application of the invention to the magneto resistance effect type magnetic head in Fig. 9, and parts in Fig. 13 corresponding to Fig. 9 are designated by the same reference numerals and the repeated description shall be omitted. In the embodiment, signal output from a low pass filter 21 is supplied to a buffer amplifier 28, and current if from the buffer amplifier 23 flows through a bias conductor

3. Negative feedback magnetic field HUB is generated from the bias conductor 3 (A separate bias conductor may be provided, and the current if may flow through the separate bias conductor.) and supplied to an MY sensing element 5.
Fig. 14 shows an equivalent circuit of the magneto resistance effect type magnetic head apparatus in Fig. 13. Based on recording signal Mix) of a traveling magnetic tape, signal magnetic field HO

HO = My em Jo (16) is generated and also feedback magnetic field -HUB is generated. Thus output voltage TV

~æ3s~2 TV = oh thy - HUB} (17) is obtained from the MY sensing element 5.
Output signal Vow I

Vow = A TV (18) is obtained from the signal taking-up means comprising circuits 16, 19, 22, 21. The feedback magnetic field -Hug is represented as follows:

-HUB = K A (it) (19) In addition, ~m(j2~/~) is transfer function at input side of the MY sensing element 5 (I : wave length), oh is transfer function at output side of the MY sensing element 5, A is transfer function of the signal taking-out means, K is transfer function of the buffer amplifier 28, and I; is transfer function of the bias conductor 3.
Fig. AYE shows resistance versus magnetic field characteristic curve of the MY sensing element 5.
If superposition magnetic field of the rectangular wave - 32 - .

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arc. magnetic field Hug of large level and the signal magnetic field HO as shown in Fig. 12B is applied to the MY sensing element 5, the output voltage Vet) as shown in Fig. 12C is obtained from the MY sensing element 5. If the output voltage TV and rectangular wave arc. signal as shown in Fig. 12D are multiplied in the multiplier 22, signal output Vow corresponding to the signal magnetic field HO in Fig. 12B is obtained at output side of the low pass filter 21.
Fig. 15 shows characteristics of second and third harmonics distortion of signal output versus record level when signal of single frequency 315 Ho is recorded on a magnetic tape and reproduced by various magnetic head apparatuses. In this case, a metal tape was used as a magnetic tape. The tape speed was 4.7 cm/sec. The recording magnetic head was usual ring type magnetic head. In the case of the MY type magnetic head apparatus, detecting current imp flowing through the MY
sensing element 5 was ma, rectangular wave arc. current it flowing through the bias conductor 3 was ma, and the frequency was 250 kHz.
In Fig. 15, curves By, By show characteristics of second and third harmonics distortion of the output ~23.~

signal by the magneto resistance effect type magnetic head apparatus in Fig. 9. It is understood that distortion in the curves Al By is considerably large in comparison to characteristics of second and third harmonics distortion of the output signal by the usual ring-shaped magnetic head apparatus shown in curves A, A.
On the contrary, curves C2, C3 show characteristics of second and third harmonics distortion of the output signal by the magneto resistance effect type magnetic head apparatus in Fig. 13. It is understood that distortion in the curves C2, C3 is as small as that of characteristics of second and third harmonics distortion of the output signal by the usual ring-shaped magnetic head apparatus shown in the curves A, Aye Next, another embodiment of the invention will be described referring to Fig. 16. The embodiment is application of the magnetic feed back of Fig. 13 to the magneto resistance effect type magnetic head apparatus in Fig. 6. Parts in Fig. 16 corresponding to Fig. 6 are designated by the same reference numerals and the repeated description shall be omitted. In the ~235~82 embodiment, signal output from a low pass filter 21 is supplied to a buffer amplifier 28, and current if from the buffer amplifier 23 flows through a bias conductor 3. Negative feedback magnetic field HUB is generated from the bias conductor 3 (A separate bias conductor may be provided, and the current if may flow through the separate bias conductor.) and applied to an MY sensing element 5. Other description shall be displaced by that of the embodiment in Fig. 13.
The magneto resistance effect type magnetic head apparatus in the embodiment comprises the magneto resistance effect sensing element to which signal magnetic field is applied, the high frequency magnetic field generating means to apply the magneto resistance effect sensing element with high frequency bias magnetic field, the signal taking-out means to take out signal output corresponding to the signal magnetic field from output of the magneto resistance effect sensing element, and the negative feedback magnetic field generating means to apply the magneto resistance effect sensing element with negative feedback magnetic field corresponding to the signal output from the signal taking-out means.

SLY

According to such constitution, in the magneto resistance effect type magnetic head apparatus to apply the magneto resistance effect sensing element with high frequency bias magnetic field, linearity is further improved and distortion is further reduced, generation of Barkhausen noise becomes little, dynamic range is further widened, and dispersion of the output becomes little.

A fifth embodiment of the invention will now be described referring to Fig. 17. In the embodiment, the above-mentioned MY head is made multi-channel structure and a part of the circuit is commonly used so as to simplify the constitution. In Fig. 17, symbols hi, ho designate first and second head elements respectively, which have first and second bias conductors 31, 32 and first and second MY sensing elements 51, 52 in similar structure to Fig. l.
Detecting do current imp flows in the first and second MY sensing elements 51. 52 which are connected in parallel (or in series) from the viewpoint of do connection. Sine wave and cosine wave signals of the so same frequency lo are supplied from a sine wave/cosine wave oscillator AYE to buffer circuits 3511 352~ and sine wave and cosine wave bias currents from the buffer circuits 251, 252 flow through the bias conductors 31 32 respectively. First and second signal magnetic fields Hal HS2 are applied to the first and second MY
sensing elements 511 52 respectively.
Numerals 16 and 19 designate a capacitor and an amplifier respectively to constitute a signal taking-out means 30. Composite outputs of the first and second MY sensing elements 51r 52 pass through the capacitor 16 commonly and are supplied to the amplifier 19. Outputs Y of the high pass filter 19 are supplied to first and second multipliers 221, 222 and multiplied with the sine wave and cosine wave signals Al, X2 respectively. The multiplied outputs Al x Y, X2 x Y are supplied to first and second low pass filters 211, 212 respectively thereby first and second output terminals 151, 152 are supplied with first and second signal outputs corresponding to the first and second signal magnetic fields HSlr HS2 applied to the first and second MY
sensing elements 51~ 52-Next, operation of the embodiment in Fig. 17 ~23S~2 will be analyzed using mathematical formulae. Assume that maximum resistance of the MY sensing element is R
maximum resistance varying rate is an, an isotropic magnetic field is Hen, amplitude of bias magnetic field is HBont signal magnetic field is Hen, and detecting currents flowing through the MY sensing elements 51t 52 are if, it (if = it). Relation of the magnetic field H
-resistance m characteristic curve in Fig. 4 is represented by following formula.

m = Rn{l-an(H - I (21~l The bias magnetic fields Hal, HB2 applied to the MY sensing elements 51, 52 are represented as follows:

Hal = Hoyle sin (it) (22) HB2 = ~B02 coy (it) (23) Frequency spectrum of Hen Hilt HS2(t)}
applied to the MY sensing elements 51r 52 has the maximum signal frequency is or less, and the bias frequency lo is selected so that lo > ifs. Then output VMRn of the MY sensing element is represented as follows:

VMRn = in x n = in~Rn{l~an(~--~ I) } (24) Calculating only variable component of the output of the MY sensing element, following formula is obtained.

VMR = yin Run an H I (25) kin Substituting the formula (2) for Ho, following formula is obtained.

-H H to (26) ~235~

When the MY sensing elements 51, 52 are connected in series, the variable component VA of the output is expressed as follows:

VA = VMRl + VMR2 = 1 1 1 Ho Hal) Hal ire 2 (HB2+ sly (27) Assuming that K1 - - fat and K2 Ho 2 formula (27) is represented as follows:

VA = Al (Hal + HSl(t))2 + K2 (HB2 + HS2 to (28) Substituting formulae (22), (23) for formula (28), the formula ~28? is expressed as follows:

~23S~

VA = K1 Gaul Senate) Hal} 2 + K2 {HB02 Cousteau) + HS2(t)}2 = Club into) + biliously Senate) + {HSl(t)~2] + K2 [H2go2 Cousteau) 2HBo2Hs2(t)coS((J~t) thus } ]
(29) The voltage VA is amplified by the amplifier (amplification factor : A). If the VA is multiplied with Senate) by the multiplier 221, the multiplying output Z, is expressed by following formula.

Al = A PA sin it = Awl [H2gol Senate) + Boyle Hal (to Senate) + {HSl(tj} 2 sin (it)]
+ AK2[H2Bo2 Cousteau) Senate) + 2HB02 HS2(t) Cousteau) Senate) + ~HS2(t)}2 Senate)] (30) If the output Al passes through the low pass filter 211 and component or more is cut off, it follows that term of Senate) O
term of Senate) 1/2 ~%35~2 term of sin it O
term of Cousteau) sin it becomes (1 - Senate)) sin it = sin it - Senate) -I O
2 cos(~t)sin(~t) = 2 Senate) O
As a result, the output Al of the filter 211 is represented by following formula.
Al = Awl- HBOl Hal (t) (31) Also the output V2 of the filter 212 is represented by following formula.

V2 = AWOKE HsO2 HS2(t) (32) Another embodiment of the invention will now be described referring to Fig. 18. Parts in Fig. 18 corresponding to Fig. 17 are designated by the same reference numerals and the repeated description shall be omitted. In the embodiment, the sine wave/cosine wave oscillator AYE in Fig. 17 is replaced by a rectangular wave generator 29B which generates first and second rectangular wave signals having the same frequency and phase difference of 90 with each other. A signal taking-out means 30 is composed of a capacitor 16 and an ~%35~2 amplifier 19. First and second multipliers 221, 222 are replaced with an inventor 24 and first and second switches 251r 252 where inverted or non-inverted output of the amplifier 19 is alternately derived by controlling the switches by the first and second rectangular signals having phase difference of 90 with each other. Outputs of the first and second change-over switches 251, 252 are supplied to first and second low pass filters 211, 212 respectively.
The MY type magnetic head apparatus in Examples 5, 6 comprises first and second magneto resistance effect sensing elements (MY sensing elements) 51r 52 to which first and second signal magnetic fields Hal HS2 are applied separately, first and second bias magnetic field generating means AYE (or 29B), 31, 32 which apply the first and second MY sensing elements 51, 52 with first and second arc. bias magnetic fields having the same frequency and phase difference of 90 with each other, a signal taking-out means 30 which takes out composite signal of signal outputs corresponding to the first and second signal magnetic fields HSlr HS2 from outputs of the first and second MY
sensing elements 51, 52, first and second multiplying - I -~235~L~2 means 221, 222 which multiply first and second arc.
signals in synchronization with the first and second arc. bias magnetic fields to the composite signal, and first and second low pass filters 211, 212 to which outputs of the first and second multiplying means 221, 222 are supplied respectively, so that first and second signal outputs corresponding to the first and second signal magnetic fields Hull HS2 are obtained from the first and second low pass filters 211, 212.
According to such constitution, the composite signal of signal outputs corresponding to the first and second signal magnetic yields is taken out from outputs of the first and second MY sensing elements 51, 52 by the common signal taking-out means 30, the composite signal is supplied to the first and second multiplying means 221, 222 and multiplied to first and second arc.
signals in synchronization with the first and second arc. bias magnetic field to be applied to the first and second MY sensing elements 51~ 52 and having the same frequency and phase difference of 90 with each other, and the multiplying outputs are supplied to the first and second low pass filters 211, 212, thereby the first and second signal outputs corresponding the first and ~23~2 second signal magnetic fields Hilt HS2 to be applied to the first and second MY sensing elements 51~ 52 are obtained separately from the first and second low pass filters 211, 212 A seventh embodiment of the invention will now be described in detail referring to Fig. 19. In the embodiment, constitution of a head element h is similar to Fig. 1 and Fig. 3 as already described Numeral 26 designates a rectangular wave generator (or sine wave generator) as arc. signal generator, and rectangular wave signal with frequency lo from the rectangular wave generator Z6 is supplied to a current driver 27 and rectangular wave current from the current driver 27 flows through a bias conductor 3.
Output from an MY sensing element 5 passes through a capacitor 16 and an amplifier 19, thereby rectangular wave signal AYE as shown in Fig. AYE is obtained at output side of the amplifier 19.
The rectangular wave signal AYE is supplied to a sample hold circuit 32 for sample hold operation.
Sample pulse signal is produced on the basis of pulse ~2354~2 signal from a pulse generator 36 and in synchronization therewith and has prescribed phase and prescribed time width. The pulse generator 36 generates pulse signal being in synchronization with rectangular wave signal from the rectangular wave generator 26 and having double frequency 2 lo in comparison to the rectangular wave signal. The pulse signal is supplied as sample pulse to the sample hold circuit. In Fig. AYE, each of symbols at, a, ..., aye, -. shows a sampling point and value on the point Output of the sample hold circuit 32 is supplied to an A/D converter 33 and converted into digital signal. The output of the A/D converter is supplied to a digital filter 34. Pulse signal from the pulse generator 36 is supplied to the A/D converter 33 and the digital filter OWE
Met, function of the digital filter 34 will be described. In the digital filter 34 as shown in Fig.
AYE, B, sign of every alternate digital value among the digital value from the A/D converter 33 corresponding to the sample values at - aye in the sample hold circuit 32, for example, the digital values corresponding to the sample values a, a, a, ... awry aye, ..., is inverted 5~8~

into the digital values corresponding to the sample values at, -a, a, -a, as, -a, ..., awry -Allah and arithmetic mean values of neighboring digital values corresponding to the inversion are taken and smoothed.
Thus output of the digital filter I becomes the digital values corresponding to the arithmetic means values b Allah - Allah by = (-a + aye, by = (a -aye, ....

b22 = (-aye + aye, b23 = (aye - aye, ..., as shown in Fig. 20B. Consequently, if the output of the digital filter 34 is converted in D/A conversion, analog signal corresponding to the signal magnetic field Ho is obtained as shown in curve 37B of Fig. 20B.
In Fig. 19, another constitution may be taken that an inventor to invert output of the amplifier, a sample hold circuit to execute sample hold operation of output of the inventor, and an A/D converter to convert output of the sample hold circuit in A/D conversion are added, rectangular wave signal from the rectangular wave generator 26 is supplied to the sample hold circuit 32 and the A/D converter 33, the rectangular wave signal from the rectangular wave generator 26 is phase-shifted by 180 and supplied to the sample hold circuit and the A/D converter both newly added, the rectangular wave ~%3S9~2 signal from the rectangular wave generator 26 and the phase-shifted signal by 180 are supplied to the digital filter 34 to which outputs of the A/D converter 33 and the newly added A/D converter are to be supplied, and arithmetic mean values of the digital values from the A/D converter 33 and the newly added A/D converter regarding neighboring values on the time axis are taken in sequence in the digital filter 34.

Another embodiment of the invention will now be described referring to Fig. 21. The embodiment relates to modification of the embodiment of Fig. 19 into multi-channel structure, and parts in Fig. 21 corresponding to Fig. 19 are designated by the same reference numerals or that with subscript regarding each channel and the repeated description shall be partially omitted.
In Fig. 21, symbols hi, ho, ..., ho designate head elements of first, second, ..., n-th channels respectively, and a bias conductor 3 is commonly used.
In sample hold circuits 321, 322, ..., 32n~ each output AYE (refer to Fig. AYE) of amplifiers 191, 192, ..., 19n - I -~2354~2 of respective channels which is supplied to the sample hold circuits 321, 322, ..., 32n is sampled and held by sampling pulse signal 42 (refer to Fig. 22B) produced on the basis of pulse signal from a pulse generator 36 with frequency 2 lo and each hold output is supplied to a multiplexer 40.
In the multiplexer 40, analog outputs 4311 432t --, 43n (difference of level neglected) in every sampling of the sample-and-hold circuits 321, 322, ....
32n are converted into serial signals located at intermediate positions between sampling pulses as shown in Fig. 22C, and then the serial signals are supplied to an A/D converter 33 and the obtained digital signals are supplied to a digital filter 34. Thus, serial signals of digital arithmetic mean signals of various channels are obtained at an output terminal 15. If output from the output terminal 15 is supplied to a demultiplexer, digital arithmetic mean signals per each channel, i.e.
digital signals corresponding to the signal magnetic fields of the MY sensing elements 51, 52, on of each channel are obtained.
In Fig. 21, sample pulses to be supplied to the sample-and-hole circuits 321, 322, ..., 32n of ~2359~2 respective channels may have different phase by a prescribed amount in sequence, and outputs of the sample-and-hold circuits 3~1r 322, --, on of respective channels are supplied to the multiplexer 40 and added there so as to obtain the serial signal (refer to Fig. 22C~.

Still another embodiment of the invention will now be described referring to Fig. 23. Parts in Fig. 23 corresponding to Fig. 19 and Fig. 21 are designated by the same reference numerals, and the repeated description shall be omitted. Outputs of amplifiers 191, 192, ..., Len of respective channels are supplied directly to integrating circuits aye, aye Noah and also through inventors 241, 242, ..., 24n to integrating circuits 451b, 452b~ 45nb- Outputs of the integrating circuits aye aye, Noah and 451b~
452b~ 45nb of the channels are supplied to sample-and-hold circuits aye, aye, ..., Noah and 321b~ 322b~
..., 32nb respectively. Outputs of the sample-and-hold circuits aye, aye, ..., Noah and 321b, 322b/ I 32nb are supplied to a multiplexer 40. Output of the US

multiplexer 40 is connected to cascade circuit of an A/D
converter 33 and a digital filter 34.
Rectangular wave signal from a rectangular wave generator 26 is supplied to a pulse generator 36 which produces two-phase rectangular wave signals being in synchronization with the rectangular wave signal from the rectangular wave generator 36 and having the same frequency and phase difference of 180 with each other.
For example, rectangular wave signal of non-inverted phase from the pulse generator 36 is supplied to the integrating circuits aye aye r Noel the sample-and-hold circuits aye, aye, ..., Noah, the multiplexer 40, the A/D converter 33 and the digital filter 34.
Also rectangular wave signal of inverted phase from the pulse generator 36 is supplied to the integrating circuits 451b~ blue --, 45nbl the sample-and-hold circuits 321b, 322b, ..., 32nb, the multiplexer 40, the A/D converter 33 and the digital filter 34.
In each output AYE (refer to Fig. AYE) of the amplifiers 191, 192, ..., l9nl portions corresponding to sample points at, a, ..., aye, ... are integrated by the integrating circuits aye aye Noah and portions corresponding to sample points a, a, ....

~2;~59~

aye, ... are integrated by the integrating circuits 451b, 452b~ 45nb-Next, operation of the integrating circuit sand the sample-and-hold circuits in Fig. 23 will be described referring to Fig. 24~ Fig. AYE shows output AYE of the amplifier, and rectangular wave signal AYE' as a part of the output AYE is formed so that integration is started by integration set pulse 53 (refer to Fig. 24D) generated at the front edge, the integration output is sampled by sample pulse 54 (refer to Fig. EYE) generated immediately before the rear edge, and integration is reset by integration reset pulse 55 (refer to Fig. 24F) generated at the rear edge Outputs of the sample-and-hold circuits aye, aye Noah; 321b~ 322b/ . . . r 32nb Of respective channels are converted into serial signals by the multiplexer 40, and then supplied to the A/D converter 33 and converted into digital signals and further supplied to the digital filter 34. In the digital filter 34, arithmetic mean value of neighboring data on the time axis is estimated regarding signal of each channel thereby serial signal of digital arithmetic mean data is obtained at an output terminal 15. The serial ~23~

signal from the output terminal 15 is supplied to a demultiplexer (not shown) and separated into data of individual channels, thereby digital signals of respective channels corresponding to the signal magnetic fields HSlr HS2r ..., Hen Of the channels are obtained.
In addition, each channel may be provided with one integrating circuit and one sample-and-hold circuit and sign inversion of every alternate sample in sample data may be effected by the multiplexer 40 or the digital filter 34.
According to the invention as above described, a magneto resistance effect type magnetic head apparatus of arc. bias system using a multiplier and a low pass filter is obtained so that circuit is formed in digital circuit and multi-channel circuit is implemented easily.
Particularly, output of the MY sensing element is integrated and then sampled and held thereby S/N
ratio of the reproduction signal can be increased.
A magneto resistance effect type magnetic head apparatus in Examples 7 and 8 comprises a magneto resistance effect sensing element (MY sensing element) 5 to which magnetic field is applied, an arc.
magnetic field generating means 3, 26 to apply the MY

~Z3~ Z

sensing element 5 with arc. bias magnetic field, sample-and-hold circuits 32 to sample and hold output of the MY
sensing element 5 in synchronization with the arc. bias magnetic field, an A/D converter 33 to effect A/D
conversion of output the sample-and-hold circuits 32, and a digital filter 34 to which the digital signals from the A/D converter 33 are supplied, whereby the digital filter 34 produces smoothed output of digital signals with sign inversion in every alternate signal in response to the signal magnetic field.
A magneto resistance effect type magnetic head apparatus in Example 9 is constituted so that outputs of MY sensing elements 51r 52~ on in the magneto resistance effect type magnetic head apparatus of Examples 7 and 8 are supplied to integrating circuits Allah Allah --, Noah and 451b, blue --l 45nbl and outputs of the integrating circuits are supplied to sample-and-hold circuits aye, aye, .--, Noah 321b~
322b, I 32nb-Consequently, in Example 7, output from the MRsensing element 5 is sampled and held in synchronization with the arc. bias magnetic field thereby multiplication is effected, and the sample hold output is supplied to 123S~

the digital filter 34 and smoothed. The digital filter 34 provides the smoothed output of digital output with sign inversion at every alternate sample in response to the signal magnetic field applied to the MY sensing element 5. Thus, as to circuit is made digital circuit, the circuit scale is not apt to become large in spite of increase of the number of channels.
In Example 8, outputs of the MY sensing elements 51, 52, .../ on are integrated and then sampled and held, thereby S/N ratio of the reproduction signal is increased.

Claims (9)

WHAT IS CLAIMED IS:

1. A magnetic transducer head utilizing magneto resistance effect comprising;
a magneto resistance effect sensing element sensing a signal magnetic field on a travelling magnetic recording medium, means for applying high frequency magnetic field to said sensing element, means for obtaining an output from said sensing element, means for rectifying said output, and low pass filter means supplied with said rectified signal for deriving an output corresponding to said signal magnetic field.

2. A magnetic transducer head utilizing magnetoresistance effect comprising;
a magnetoresistance effect sensing element sensing a signal magnetic field on a traveling magnetic recording medium, means for deriving high frequency signal, means for applying high frequency magnetic field synchronized with said high frequency signal to said sensing element, means for obtaining an output from said sensing element, means for multiplying said output with said high frequency signal to derive a multiplied signal, and low pass filter means supplied with said multiplied signal for deriving an output corresponding to said signal magnetic field.

3. A magnetic transducer head according to claims 1 or 2, further comprises feed back means of said output corresponding to said signal magnetic field to said means for applying high frequency magnetic field to said sensing element.

4. A magnetic transducer head utilizing magnetoresistance effect comprising;
a first and a second magnetoresistance effect sensing elements, each sensing a first and second signal magnetic field respectively, first means for deriving a first high frequency signal, second means for deriving a second high frequency signal having a phase difference of .pi./4 from said first high frequency signal, means for applying high frequency magnetic field synchronized with said first and said second high frequency signal to said first and said second sensing element respectively, means for obtaining a composite output from said first and said second sensing element, first means for multiplying said composite output with said first high frequency signal to derive a first multiplied signal first low pass filter means supplied with said first multiplied signal for deriving an output corresponding to said first signal magnetic field, second means for multiplying said composite output with said second high frequency signal, to derive a second multiplied signal, and second low pass filter means supplied with said second multiplied signal for deriving an output corresponding to said second signal magnetic field.

5. A magnetic transducer head according to claims 1, 2 or 4, said means for deriving high frequency signal is a high frequency rectangular wave generator.

6. A magnetic transducer head according to claims 1, 2 or 4, said high frequency magnetic field is generated by a high frequency current flow synchronized with said high frequency signal through a conductor provided adjacent to said sensing element.

7. A magnetic transducer head according to claim 2, said means for multiplying it carried out by sequencially deriving said output and an inverted signal of said output alternately switching synchronized with said high frequency signal.

8. A magnetic transducer head according to claim 1, said high frequency magnetic field is applied by a high frequency current flow through a conductor provided adjacent to sensing element

9. A magnetic transducer head according to claim 1, said multiplied signal is obtained by multiplying said output and said high frequency current.